Liquid silicon rubber with low compression set

Abstract

The invention relates to compositions which crosslink to give elastomers and are based on component (A) comprising polyorganosiloxane (I) with at least two alkenyl groups per molecule and component (B) comprising polyorganosiloxane (II) with at least two silicon-bonded hydrogen atoms and organic per oxide (III).

What is claimed is: 
     
       1. A two component, addition crosslinkable organopolysiloxane composition which exhibits increased reproducibility after storage prior to cure, comprising: A) a first component comprising A) 1) one or more organopolysiloxanes containing two or more alkenyl groups per molecule and   A) 2) a metallic hydrosilylation catalyst; and     B) a second component comprising: B) 1) one or more organopolysiloxanes containing two or more Si--H bonded hydrogen atoms per molecule   B) 2) from 0.01 to 0.19 weight percent of an organic peroxide, said weight percent relative to the total weight of components A) and B).     
     
     
       2. The two component, addition-crosslinkable organopolysiloxane composition of claim 1, wherein component B) further comprises one or more alkenyl-functional organopolysiloxanes. 
     
     
       3. The composition of claim 1, wherein said organic peroxide is 2.5-dimethyl-2,5-bis(tert-butylperoxy)hexane. 
     
     
       4. The two component, addition crosslinkable organopolysiloxane composition of claim 1 wherein said organic peroxide is present in an amount of from about 0.01 to about 0.1 weight percent. 
     
     
       5. The two component, addition crosslinkable organopolysiloxane of claim 4 wherein said organopolysiloxanes containing two or more alkenyl groups have a viscosity of 500 Pa·s or less. 
     
     
       6. A process for preparing an organopolysiloxane elastomer, comprising mixing component A) and component B) of claim 1 and curing to form an addition-crosslinked elastomer. 
     
     
       7. The composition of claim 1, wherein said organic peroxide is dicumylperoxide.